1. Field of the Invention
The present invention relates to a telescopic column, especially for height-adjustable tables.
2. The Prior Art
For convenience, the disclosure of the invention will be based on lifting columns for height-adjustable tables driven by an electric motor. The lifting columns may be categorized according to the mechanical elements which are used for causing the telescopic movement. Some are based on spindles, others on endless chains, and some on racks. The invention is related to the last-mentioned category. DE 44 17 337 to Christof Stoll GmbH discloses a table structure having a column at each side, where each column has a drive motor for moving the telescopic member. In order to synchronize the two columns, the telescopic members are provided with a toothing and with a through shaft having a gear wheel at each end, in mesh with the toothing the movement of the telescopic members is thereby synchronized. DE 37 109 012 to Ergonomic Equipment Pty. Ltd. discloses a table likewise having a column at each side, where the telescopic member is provided with a rack. The telescopic members may be moved manually by a flywheel or by a motor, which drives a through shaft having a gear wheel at each end in mesh with the racks. In the first-mentioned structure, the toothing is visible, which is undesirable, and the second structure requires a long slot, since the rack is arranged inside the telescopic members. EP 1 026 972 to Actuall B. V. discloses a structure having four racks which, in pairs, are in mesh with a shaft having a gear wheel at each end. The one shaft is driven by an electric motor for moving the telescopic member. The structure is complicated and requires a quadrangular cross-section of the column. EP 1 018 312 to Actuall B. V., FIGS. 2a and b, discloses a column having two racks disposed opposite each other on the internal side of the outermost member of the column, while a drive unit having gear wheels in mesh with the racks is arranged inside the innermost member of the column. FIGS. 1a and b show a drive unit according to the same principle, but with the telescopic member disposed at the side of the stationary member. The stated structures are relatively complicated and expensive.
The object of the invention is to obviate the problems mentioned above.